Light sensitive electrode



Patented May 27, 194i LIGHT SENSITIVE ELECTRODE Hans Gerhard Lubszynski, Hillingdon, and

Leonard Klatzow, London, England, assignors to Electric & Musical IndustriesV Limited, Hayes, Middlesex, England, a company of Great Britain Application March io, 193s, serial No. 195,196

in Great Britain March 10, 1937 Y Claims.

The present invention relates to transparent light sensitive electrodes and methods of Inaking the same.

Transparent light sensitive electrodes usually comprise a transparent carrier, usually of glass or mica, on which is deposited an electrode layer which is thin enough to be transparent. The electrode layer is rendered light sensitive in any suitable way.

It is frequently of advantage to arrange a transparent light sensitive electrode to be highly sensitive to light incident on it through the supporting carrier, that is, incident on the back of the electrode.

It is thus desirable to position the light sensitive region of the electrode coating as near to the carrier as possible. However, the electrode is usually required to be continuously electrically conductive over its surface, and for this purpose it must be rendered much thicker than the light sensitive layer itself. If the light sensitive portion of the electrode is on the face nearest the anode, the thickened electrode tends to absorb light before the light sensitive layer is reached, thereby reducing the eiective light-sensitivity oi the electrode.

The object of the invention is to provide a highly transparent photo-electrically active electrode of high sensitivity and in which the light sensitive layer is continuously electrically conductive.

In describing the invention in detail, reference will be made to the drawing in which Fig. 1 shows in block diagram form the steps in the method of preparing the new and novel light sensitive electrode in accordance with the invention, While Fig. 2 shows schematically the electrode structure prepared in accordance with the method steps outlined in Fig. 1.

According to the invention a method of making a transparent light sensitive electrode is provided comprising first, step 1, depositing on a suitable transparent carrier a thin layer of a material which is adapted to be oxidised and then rendered sensitive to light, the layer being so thin (Cl. Z50-27.5)

and a further layer of silver being applied over the oxidised layer to render it conductive, the thin layer being treated with caesium vapour to render it light sensitive before or after deposition of the thick layer. For the best results, it appears that the thickness of the thin initial layer of silver should be of the order of ten molecular layers.

A photo-electric tube constructed according to the invention, in which the sensitising operation was performed after the deposition of a thick layer was found to have a sensitivity of about 'iO/ia/lumen, with the light falling on the side of the cathode remote from the anode. The tube may take any form and is conveniently designed to intercept as much light as possible.

It is preferred to sensitise the tube after deposition of the relatively thick layer, as in this case, as the electrode is made electrically conducting before being sensitised it is possible to measure the sensitivity of the electrode while it is being sensitised.

In Fig. 2 the electrode structure is shown dagrammatically in which 2l shows the transparent support member, 23 shows the photosensitized oxidized layer and 25 shows the conducting layer whose thickness is greater than that of the photosensitized oxidized layer 23.

As the light sensitive electrode in a transparent tube embodying the invention, has the thin oxidised layer as near the carrier as possible, very little light energy is lost before the region of the electrode is reached at which the light is effective in producing the desired photo-electric effect. Moreover, this advantage is achieved Without sacrice of the conductivity of the electrode, as the deposition of the relatively thick layer of silver or other conductive material ensures that the electrode is sufficiently conducting for the negative charges on the cathodic surface produced by the loss of electrons, to be effective in any external circuit.

A further advantage oi a tube embodying the invention with a caesium treated oxidised silver and silver light sensitive electrode as cathode, is found to be that the thermionic emission from the cathode is extremely small, being of the order of a thousand times less than from a normal opaque cathodic layer of silver oxide treated with caesium.

We claim:

1. The method of preparing a. transparent light sensitive electrode which comprises the steps of depositing a transparent, electrically non-conducting continuous layer of metal upon a sup.

porting surface, oxidizing the deposited metal layer, photosensitizing the deposited layer, depositing upon the photosensitized layer a transparent continuous electrically conducting layer of metal and continuing the deposition until the thickness of the metal layer is greater than that of the photosensitized layer.

2. The method of preparing a transparent light sensitive electrode, which comprises the steps of depositing a transparent electrically non-conducting metallic layer upon ya supporting surface, oxidizing the deposited` layer, depositing a transparent, continuously-electrically conducting, layer of metal upon the oxidized layer, and subsequently photosensitizing the oxidized layer.

3. The method of preparing a transparent light sensitive electrode, which comprises the steps of depositing a transparent, electrically nonconducting continuous layer of silver upon a supporting surface, oxidizing the deposited layerof silver, yphotosensitizing the oxidized layer, and depositing a transparent continuously electrically defiance conducting layer oi silver upon the oxidized layei" of silver.

4. The method of preparing a transparent light sensitive electrode which comprises the steps of depositing a transparent, electrically nonconducting laye-1' of silver upon a supporting surface, oxidizing the deposited layer of silver, depositing a transparent, continuously electrically-conducting, layer of silver upon the oxidized layer of silver, and subsequently photosensitizing the oxidized layer.

5. A photosensitive electrode comprising a continuous transparent supporting surface, a transparent layer of caesium-activated, oxidized silver, deposited upon said supporting surface, and a transparent continuously electrically conducting layer of silver deposited upon the activated layer, said electrically conducting layer being thick relative to the caesium activated layer.

HANS GERHARD LUBSZYNSKI. LEONARD KLATZOW. 

